This film is Psycho turned inside out, in several ways. The gender of the killer is switched from male to female. The setting is switched from rural to urban.
Those might be coincidences. The real difference is that we're inside the crazy killer's mind, rather than outside: we see life from her perspective. More information, more empathy. At the same time, we get much less explanation - much less understanding - than Hitchcock gives us in Psycho.
Take the final images. In Psycho it's the famous shot of the dead mother: horrifying but at the same time revelatory. We know what Norman Bates is all about when the film ends. Here the final shot is a long tracking shot through the house, a shot that itself encapsulates the whole film's rising tension. The camera quests through the debris, just slowly enough for the eye to pick out seemingly significant details - the ticking clock, the childhood toys - but still fast enough for us to feel that the camera is telling us these items don't explain anything. It's the movement that's significant, an incessant denial of closure that counteracts any understanding we think we're getting from the gradual but insistent tightening of the focus. Finally the camera comes to rest on the old family photo - we think we're going to get an answer now (what's the question? why this girl went mad), but the camera keeps zooming in - the tightening focus now becomes the movement denying us answers. Is it something in her family life, her childhood, that drove her mad? That's what we think at first, but the camera keeps zooming in on this photo, closer and closer, until we no longer see the family all at once but the girl alone (and even when we see the whole photo we notice that shadows cut the girl off from the rest) - maybe family isn't the explanation - maybe it's all in her head - and we zoom in on her head, closer and closer, then her eye, and by this time we're dissolving into the grain of the photo. There's no end to the movement, no end to the search for answers - because the film can find no answers. Why does she go mad? We don't know: she just does.